In process plants, field devices that sense or control parameters for processing chemicals and pharmaceuticals are smart devices. A smart device is a measurement and/or control module with a transmitter that can communicate with host devices over a wired or wireless communication channel using one or more standard protocols. “Transmitter” is often synonymous with smart device.
Host devices include computers, calibrators, communicators, tablets and personal digital assistants. Some standard protocols are HART, an acronym for Highway Addressable Remote Transducer, or FOUNDATION Fieldbus. HART is an industry standard for a hybrid protocol that enables communications between smart field devices and a control system that employs legacy 4-20 mA wiring. FOUNDATION Fieldbus is an all-digital protocol. Other protocols are PROFIBUS and PROFINET International.
A smart device with the HART protocol has a microprocessor and one or more memories. The memories hold data about the manufacturer of the device, its current readings for a primary variable, other variables, and ranges of one or more variables. The microprocessor is programmed to perform a number of specific operations and to respond to predetermined commands. Such commands include and are not limited to reading manufacturer information, reading a primary variable (e.g., pressure), and reading one or more secondary variables (e.g., temperature). Other commands are used to configure the smart device, including and not limited to setting the range of the measured variables, including their upper and lower range limits.
A smart device has one or more transducers that measure physical parameters, such as pressure or temperature or control whether a valve is open or closed and the percentage of how much the valve is open. Transducers convert a signal of a parameter in one form of energy (e.g., pressure, flow) into electrical signals. The output of the transducer is converted from analog to digital values by an analog-to-digital converter whose output is input to a microprocessor. Some smart devices may have a microprocessor and circuitry for performing A-to-D and A-to-D conversion in a single chip. Depending upon the type of communication network, the microprocessor output may be converted into an analog value for transmission via a wired or wireless transmitter.
A smart device stores many types of information in its memory. For example, a smart device also stores the units of the primary variable of the device, the lower range value, upper range value, damping, and transfer functions. Smart devices also store tag information to identify the device by its location in the process, its function, and information identifying the manufacture, model, and revision of the smart device. The tag information is in the memory of the smart device. The tag parameter/field is entered in the smart device by the end user. A host, such as a calibrator or communicator, uses universal commands to locate and read tag information.
In order to access information and settings in the smart device, such as primary, secondary, and other variables and parameters, each smart device is associated with a Device Description (DD). The DD describes the capabilities of a smart device. The DD is organized in a hierarchical structure (tree) of read-only parameters, read/write parameters, standard operating procedures (methods), and other information for use by a communication host. A DD has menus and graphic display features that are used by host applications (including handheld calibrators, communicators, and other hosts) to access all parameters and data in the corresponding smart device. A DD is typically written by the manufacturer of a smart device. The specifications for a DD are controlled by standards bodies such as IEC and ISA with contributions from HART Communication Foundation, Fieldbus Foundation, PROFIBUS and PROFINET International.
The DD is an electronic data file stored in a host device, such as a communicator. A DD comprises multiple levels and is arranged in the tree-like structure with branches between levels. A DD is similar to a database of information about the device, and includes algorithms for use when attempting to accomplish specific tasks with the device, such as sensor trim, and locations in the smart device where information is stored. DDs provide the information needed by a host such as a communicator, calibrator, host application, or control system to properly access device information and display device information located in smart devices.
A DD and its menu structure are unique to a device and a device revision. A DD for one device cannot be used with a completely different device from another manufacturer, even if that other device were to offer the same functionality. However, DDs do support multi-vendor interoperability. Each device may be configured to specific parameters so that process managers may configure transmitters from one manufacturer to replace a device from another manufacturer. The DD does not contain any information about current values in a smart device but enables a host to read the memory of the device and to acquire items of device information that are stored in the device transmitter.
The DD declares or explains a device such as a smart device transmitter. Actual processing is done by communication host devices such as communicators or calibrators. A communication host uses a DD to communicate with a smart device. A communication host is capable of communicating with smart devices using one or more protocols. A host has the ability to display various parametric values and allows the user to set configuration parameters on such transmitters. A host may use DDs that persist in the host's storage memory, in order to provide access to the full capabilities, as described by the provider of the DD, of that smart device.
A conventional communicator has a display, a numerical keypad, function buttons, and navigation buttons for moving from one menu to the next, through menus, and left or right and up and down in a given menu. In some embodiments, the communicator has input and output communication ports that are connected via cables or wirelessly to the smart device. When a communicator is connected to a smart device, the communicator uses a DD for the smart device to access parameters and other data stored in the memory of the smart device. The communicator has a DD interpreter file that is executable to allow the technician to navigate from the entry level to any location in the in the memory of the smart device.
Many smart devices have hundreds of different parameters. Using a DD, one may follow its intricate structure to reach any or all of the locations in the smart device that hold parameters. However, DDs are arranged in multiple-branched levels. Each level may hold one or more potential preferred parameters. In order to reach each location, one must begin at the start of the DD structure and follow its path to each parameter. When parameters are in different branches, one cannot jump from one parameter to another without navigating up the DD hierarchy.
Technicians perform inspections, maintenance, tests, and troubleshoot smart devices in the process plant. They access data from the smart devices with a handheld instrument such as a communicator. Communicators use DDs to inspect and configure smart devices. Configuration means using the communication protocol to change settings inside the smart device. Although a communicator can be used for configuration and checking diagnostic information, it cannot be used for calibration to check the measurement accuracy of a smart device. Configuring parameters of a HART transmitter with a communicator is not calibration and does not assure accuracy. For a true calibration, a reference standard is always needed.
Technicians who inspect smart devices often repeatedly inspect the same parameters for a given device and may configure those same parameters as needed. For each parameter to be inspected, the technician must start from the beginning of the DD structure and navigate through the smart device to the location of the desired parameter. As such, routine inspections are tedious and time-consuming.
Because the same parameters are often repeatedly inspected and configured, inspection and configuration are tedious, repetitive, and time consuming. There has been a long-felt need and unmet need for a communicator that rapidly accesses certain parameters, reads, records, and reconfigures the parameters without navigating along the intricate DD data structure.